1. Field of the Invention
The present invention relates to a seat structure in which a combination of a two- or three-dimensional net having a large hysteresis loss and metal springs having a small hysteresis loss is employed to enhance the vibration absorptivity and the posture supporting or holding properties.
2. Description of the Related Art
Conventional automobile seats generally include spring members attached to a seat frame, a pad material such as a foam material or cotton placed thereon, and a skin such as a vinyl leather, woven cloth, or leather covered thereon. On the other hand, seats other than automobile seats generally include a pad material placed on the frame and covered with a skin, and some of them also include spring members for enhancing the cushioning characteristics. Although the spring members or the pad material acts to provide desired cushioning characteristics, conventional seats are mostly thick, heavy and costly.
In view of the above, a variety of lightweight, inexpensive and thin seats have recently been proposed, and the inventors of this application have developed thin seats having a lightweight net of a three-dimensional structure that is provided with desired characteristics (spring properties, damping characteristics and the like) sufficient for a cushioning material.
A three-dimensional net (hereinafter referred to as 3-D net) as employed in such thin seats is formed of a three-dimensional knit fabric, which has a ground fabric formed into, for example, a knit texture or a honeycomb-shaped (hexagonal) mesh. The 3-D net has a three-layered solid truss structure in which an upper mesh layer and a lower mesh layer are connected to each other by a pile layer having a large number of piles. Each yarn of the upper mesh layer and the lower mesh layer is formed by twisting a number of fine threads, while each of the piles is formed of a single thick string to provide the three-dimensional knit fabric with rigidity.
However, in the case where the 3-D net is employed in automobile seats, a user sometimes feels a pain or a strong pressure on his or her legs or thighs when getting in or out of the automobile or operating pedals. Even in the case where the 3D net is employed in seats other than the automobile seats, the user sometimes feels a similar pain.